Wind funnel, Science Project

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Wind funnel

Light a candle and blow at it hard through a funnel held with its mouth a little way from the flame. You cannot blow out the flame; on the contrary it moves towards the funnel. When you blow through the funnel the air pressure inside is reduced, and so the air outside enters the space through the mouth. The blow air sweeps along the funnel walls: if you hold the funnel with the edge directly in front of the flame, it goes out. If you blow the candle through the mouth of the funnel, the air is compressed in the narrow spout, and extinguishes the flame immediately on exit.

Floating card, Science Project

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Floating card

Many physical experiments seem like magic, but there are logical explanations and laws for all the strange occurrences. Stick a thumbtack through the middle of a halved postcard. Hold it under a cotton spool so that the pin projects into the hole and blow hard down the hole. If you manage to loosen the card, you really expect into fall. In fact, it remains hovering under the spool. Bernoulli’s law explains this surprising result. The air current goes through at high speed between the card and the spool, producing a lower pressure, and the normal air pressure pushes the card from below against the spool. The ascent of an aeroplane takes place in a similar manner. The air flows over the arched upper surface of the wings faster than over the flat under-surface, and therefore the air pressure above the wings is reduced.

Flying coin, Science Project

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Flying coin

Lay a sixpence or a dime four inches from the edge of the table and place a shallow dish eight: inches beyond it. How can you blow the coin into the dish! You will never do it if you blow at the coin from the front - on the false assumption that the air will be blown under the coin because of the unevenness of the table and lift it up. It will only be transferred to the dish if you blow once sharply about two inches horizontally above it. The air pressure above the coin is reduced, the surrounding air, which is at normal pressure, flows in from  all directions and lifts the coin. It goes into the air current and spins into the dish.

Trapped ball, Science Project

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Trapped ball

Place a table tennis ball in a funnel, hold it with the mouth sloping upwards, and blow as hard as you can through the spout. You would hardly believe it, but nobody can manage to blow the ball

out. The air current does not hit the ball, as one would assume, with its full force. It separates and pushes through the places where the ball rests on the funnel. At these points the air pressure is lowered according to Bernoulli’s law, and the external air pressure pushes the ball firmly into the mouth of the funnel.

Wind-proof coin, Science Project

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Wind-proof coin

Push three pins into the middle of a piece of wood and lay a coin (5 new pence or 25-cents) on top of them. You can make a bet! Nobody who does not know the experiment will be able to blow the coin off the tripod. The metal cannot hold the gust of air on its narrow, smooth edges. The gust shoots through under the coin and reduces the air pressure, forcing the coin more firmly on to the pins. But if you lay your chin on the wood just in front of the coin and blow with your lower lip pushed forward, the air hits the underside of the coin directly and lifts it off.

Bernoulli was right, Science Project

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Bernoulli was right

Lay a postcard bent lengthways on the table. You would certainly think that it would be easy to overturn the card if you blew hard underneath it. Try it! However hard you blow, the card will not rise from the table. On the contrary, it clings more firmly. Daniel Bernoulli, a Swiss scientist of the eighteenth century, discovered that the pressure of a gas is lower at higher speed. The air stream produces a lower pressure under the card, so that the normal air pressure above presses the card on to the table.

Curious air currents, Science Project

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Curious air currents

If you stand behind a tree trunk or a round pillar on a windy day, you will notice that if offers no protection, and a lighted match will be extinguished. A small experiment at home will confirm this: blow hard against a bottle which has a burning candle standing behind it, and the flame goes out at once. The air current divides on hitting the bottle, clings to the sides, and joins up again behind the bottle with its strength hardly reduced. It forms an eddy which hits the flame. You can put out a lighted candle placed behind two bottles in this way, if you have a good blow.

Egg blowing, Science Project

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Egg blowing

Place two porcelain egg-cups one in front of the other, with an egg in the front one. Blow hard from above on to the edge of the filled cup. Suddenly the egg rises, turns upside down and falls into the empty cup. Because the egg shell is rough, it does nor lie flat against the smooth wall of the egg-cup. Air is blown through the gap into the space under the egg, where it becomes compressed. When the pressure of the cushion is great enough, it lifts the egg upwards.

Compressed air rocket, Science Project

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Compressed air rocket

Bore a hole through the cap of a plastic bottle, push a plastic drinking straw through it and seal the joints with adhesive. This is the launching pad. Make the rocket from a four-inch-long straw,

which must slide smoothly over the plastic straw. Stick coloured paper triangles for the tail unit at one end of the straw, and at the other end plasticine as the head. Now push the plastic tube into

the rocket until its tip sticks lightly into the plasticine. If you press hard on the bottle the projectile will fly a distance of 10 yards or more. When you press the plastic bottle, the air inside is compressed. When the pressure is great enough, the plastic straw is released from the plug of plasticine, the released air expands again, and shoots off the projectile. The plasticine has the same function as the discharge mechanism in an airgun.

Blowing trick, Science Project

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Blowing trick

Place a playing card on a wineglass so that at the side only a small gap remains. Lay a large coin (half a dollar or 10 new pence) on the card. The task is to get the coin into the glass. Anybody who does not know the trick will try to blow the coin into the gap from the side without success.

The experiment only works if you blow once quickly into the mouth of the glass. The air is trapped inside and compressed. The increased pressure lifts the card and the coin slides over it and into the glass.

Shooting backwards, Science Project

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Shooting backwards

Hold an empty bottle horizontal and place a small paper ball lust inside its neck. Try to blow the ball into the bottle. You cannot! Instead of going into the bottle, the ball flies towards your face. When you blow, the air pressure in the bottle is increased, and at the same time there is a partial vacuum just inside the neck. The pressures become equalised so that the ball is driven out as from an airgun.

Match lift, Science Project

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Match lift

It is simple, using air, to lift matches from the table into their box. Hold the case between your lips and lower it over the matches. Draw a deep breath, and the matches hang on to the bottom of the case as though they were stuck on. By drawing in breath you produce a dilution of the air, in the case. Air pressure pushes the matches from underneath towards the opening. Even a single match can be raised in this way, if the air is drawn in sharply.

Fountain, Science Project

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Fountain

Punch two holes in the lid of a jam jar and push a plastic straw a distance of two Inches through one. Fix three more straws together with adhesive tape and push through the other hole. Seal the joints with warm plasticine. Screw the lid to the jar, which should contain some water, turn it upside down and let the short straw dip into a bottle full of water: a fountain of water rises into the upper jar until the bottle is empty. The water pours out through the long tube, and the air pressure in the jar becomes less. The air outside tries to get in and pushes the water from the bottle.

Weather frog, Science Project

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Weather frog

A tree frog made of paper will climb up and down a ladder like a real weather frog and predict the weather. Bend a 2f-inch-long strip of metal into a U-shape and bore through it so that a sewing needle can be turned easily when inserted through the holes. The needle is made able to grip by heating, and the frog, made from green paper, is fixed on to it by a thin wire. Stick the metal strip firmly on to the middle of the wall of a four-inch-high jar, and at the side a cardboard ladder. Wind a thread round the needle, with a small counterweight at the end. Stick a paper disk on a piece of plastic foil, and draw the other end of the thread through the middle. The foil is stretched over the mouth of the jar so as to be smooth and airtight, the thread is tightly knotted, and the hole sealed. When the air pressure is high (fine weather) the plastic foil is pressed inwards and the frog climbs up. When the pressure is low (bad weather) the pressure on the foil is less and the frog climbs back down.

Bottle barometer , Science Project

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Bottle barometer

Stretch a piece of balloon rubber over the mouth of a milk bottle and stick a straw on top of it. As the air pressure varies daily according to the state of the weather, the end of the straw moves up and down. When the air pressure is higher in fine weather, the rubber is pressed inwards, and the end of the pointer rises. When the air pressure falls, the pressure on the rubber is reduced, and the pointer falls. Because the air in the bottle will expand if it is heated, the barometer should be placed in a spot where the temperature will remain constant.

Weight of air on paper, Science Project

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Weight of air on paper

Lay a cigar-box lid over the edge of a smooth table. Spread an undamaged sheet of newspaper and smooth it firmly on to the lid. Hit the projecting part of the lid hard with your fist. It breaks, without the paper flying up. The lid is only slightly tilted when it is hit. In the space formed between the lid, newspaper and table, the air cannot flow in quickly enough, so that there is a partial vacuum, and the normal air pressure above holds the lid still as if it were in a screw clamp.

Hanging water, Science Project

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Hanging water

Fill a glass to overflowing with water and lay a post cardon it. Support the card with one hand, turn the glass upside down and remove your hand from the card. it remains on the glass, and allows no water to escape.With a glass of normal height, a weight of water of about 2 ounces presses on each square inch of card. On the other hand the pressure of air from below is about one- hundred times as great on

each square inch, and presses the card so firmly against the glass that no air can enter at the side and so no water can flow out

Air lock, Science Project

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Air lock

Place a funnel with not too wide a spout into the mouth of a bottle and seal it with plasticine so that it is airtight. If you pour some water into the funnel, it will not flow into the bottle. The air enclosed in the bottle prevents the water entering. On the other hand, the water particles at the mouth of the funnel, compressed like a skin by surface tension, do not allow any air to escape. Close one end of a straw, push the other end through the funnel, lift your finger, and the water flows at once into the bottle. The air can now escape through the straw.

Balloon in the bottle, Science Project

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Balloon in the bottle

Do you believe that it is always possible to blow an ordinary balloon right up! You will be surprised: push a balloon into a bottle and stretch its mouth-piece over the opening. Blow hard into the balloon. It is only possible to stretch the rubber before your breath runs out. As the pressure of the air in the balloon increases, so does the counter-pressure of the air enclosed in the bottle. It is soon so great that the breathing muscles in your thorax are not strong enough to

overcome it.

Diving bell , Science Project

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Diving bell

You can immerse a pocket-handkerchief in water, without it getting wet: stuff the handkerchief firmly into a tumbler and immerse it upside down in the water. Air is certainly invisible, but it nevertheless consists of minute particles, which fill the available space. So air is also enclosed in the upturned glass, and it stops the water entering. If, however, you push the glass deeper, you will see that some water does enter, due to the increasing water pressure, which compresses the air slightly. Diving bells and caissons, used under water, work on the same principle.

Magnetic ducks science project

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Magnetic ducks

Make two ducks from paper doubled over and glued and push a magnetised pin into each one. Place the ducks on cork disks in a dish of water. After moving around they line up with their beaks or tail tips together in a north-south direction. The ducks approach each other along the magnetic field lines. Their movement is caused by different forces: the attraction of unlike magnetic poles, the repelling effect of like poles, and the earth’s magnetism. Set the magnets so that two poles which will be attracted are placed in the beaks.

Dip to the pole, science project

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Dip to the pole

Magnetise two steel pins so that their points attract each other strongly. Push them into the ends of a piece of foam plastic about as thick as a pencil and balance this by means of a sewing needle over two tumblers (by shifting the pins and pulling off pieces of plastic), if you allow this compass to swing in a north-south direction, it will come to rest with the end facing north sloping downwards. The compass needle comes to rest parallel to the magnetic field lines, which span the earth from pole to pole. This deviation (dip) from the horizontal is 670 in London, 720 in New York. 600 in Los Angeles and at the magnetic poles of the earth 900.

Compass needle

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Compass needle

Stroke a sewing needle with a magnet until it is magnetised and push it through a cork disk. Put the needle into a transparent plastic lid containing water and it turns in a northsouth direction. Stick a paper compass card under the lid. The needle points towards the magnetic North pole of the earth. This lies in North Canada and is not to be confused with the geographical North Pole,

round which our earth rotates. The deviation (declination) of the magnetic needle from the true

north is 80 in London and 150 in New York (in a westerly direction) and l0 in Chicago and 150 in Los Angeles, (in an easterly direction).

Magnetic or not.

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Magnetic or not?

Many iron and steel objects are magnetised without one realising it. You can detect this magnetism with a compass. If a rod is magnetised, it must, like the compass needle, have a north and South Pole. Since two unlike poles attract and two like poles repel, one pole of the needle will be attracted to the end of the bar and the other repelled. If the bar is not magnetised, both poles of the needle are attracted to the end.

The earth’s magnetic field, Science Project

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The earth’s magnetic field

Hold a soft iron bar pointing to the north and sloping downwards, and hammer it several times. It will become slightly magnetic. The earth is surrounded by magnetic field lines, which meet the

earth in Great Britain and North America at an angle between 60 and 80-degrees. When the iron is hammered, its magnet particles are affected by the earth’s magnetic field lines and point to the north. In a similar way, tools sometimes become magnetic for no apparent reason. If you hold a magnetised bar in an east-west direction and hammer it, it loses its magnetism.

Magnetism Field lines, Science Project

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Magnetism Field lines

Lay a sheet of drawing paper over a magnet - of course you already know how to make a magnet - and scatter iron filings on it. Tap the paper lightly, and a pattern forms. The filings form into curved lines and show the direction of the magnetic force. You can make the pattern permanent. Dip the paper into melted candle wax and let it cool. Scatter the iron filings on it. If you hold a hot iron over the paper after the formation of the magnetic lines, the field lines, the pattern will be fixed.

Electric light, Science Project

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Electric light

In many homes there is a voltage tester, generally in the form of a screwdriver. In its handle there is, amongst other things, a small neon tube, which you can easily remove. Hold one metal end firmly and rub the other on a piece of hard foam plastic which may be used for insulation. The lamp begins to glow as it is rubbed to and fro, and you can see this particularly clearly in the dark. Since the plastic is soft, its layers are rubbed against one another by the movement of the lamp and become strongly charged with electricity. The electrons collect on the surface, flow through the core of the tiny lamp, which begins to glow and into the body. The ancient Greeks had already discovered that amber attracted other substances when it was rubbed. They called the petrified resin ‘electron’. The power, which has caused such fundamental changes in the world since then therefore, gets its name - electricity.

Flash of lightning, Science Project

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Flash of lightning

Place a metal slice on dry glass, and on it a piece of hard foam plastic which you have rubbed well on your pullover. If you hold your finger near the handle of the slice, a spark jumps across.

When the negatively charged plastic is placed on the slice, the negative electric particles in the metal are repelled to the end of the handle, and the voltage between it and the finger becomes equalised. Plastic materials can become strongly charged. In warehouses, for example, metal stands for rolls of plastic are earthed because otherwise they often spark when by the personnel.

High voltage, Science Project

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High voltage

Place a flat baking tray on a dry glass, rub a blown-up balloon vigorously on a woollen pullover and place it on the tray. If you put your finger near the edge of the tray, a spark jumps across. A voltage equalisation occurs between the metal and the finger. Although the spark is discharged with several thousand volts, it is just as harmless as the sparks produced when you comb your hair. An American scientist discovered that a cat’s fur must be stroked 9,200.000.000 times to produce a current sufficient to light a 75-watt bulb for a minute.

Puppet dance, Science Project

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Puppet dance

Lay a pane of glass across two books, with a metal plate underneath. Cut out dolls an inch or so high from tissue paper. If you rub the glass with a woollen cloth, the dolls underneath begin a lively dance. They stand up, turn round in a circle, fall, and spring up again. The glass becomes electrically charged when it is rubbed with the wool, attracts the dolls, and also charges them. Since the two like charges repel each other, the dolls fall back on the plate, give up their charge to the metal and are again attracted to the glass.

Electric fleas, Science Project

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Electric fleas

Rub a long-playing record with a woollen cloth and place it on a glass. If you toss some small silver-paper balls on to the record, they will jump away from one another in a zigzag motion. If you then move the balls together with your fingers, they will hop fiercely away again. The electricity produced on the record by rubbing is distributed in irregular fields. The balls take up the charge and are repelled, but are again attracted to fields with the opposite charge. They will also be repelled when they meet balls with the same charge.

Electrical ball game, Science Project

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Electrical ball game

Fix a piece of silver paper cut into the shape of a footballer on to the edge of a phonograph record, rub the record vigorously with a woollen cloth and place it on a dry glass. Put a tin can about two inches in front of the figure. If you hold a small silver-paper ball on a thread between them, it swings repeatedly from the figure to the can and back. The electric charge on the record flows into the silver-paper figure and attracts the ball, it becomes charged, but is immediately repelled because the charges become equal, and goes to the can, where it loses its electricity. This process is repeated for a time.

Simple electroscope, Science Project

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Simple electroscope

Bore a hole through the lid of a jam jar and push a piece of copper wire bent into a hook through it. Hang a folded strip of silver paper, from which you have removed the paper, over the back. If you hold a fountain pen, comb, or similar object, which has been electrically charged by rubbing on the top of the wire, the ends of the strip spring apart. On contact with a charged object, electrical charges flow through the wire to the ends of the strip. Both now have the same charge and repel one another according to the strength of the charge.

Shooting puffed rice, Science Project

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Shooting puffed rice

Charge a plastic spoon with a woollen cloth and hold it over a dish containing puffed rice. The grains jump up and remain hanging on the spoon until suddenly they shoot wildly in all directions. The puffed rice grains are attracted to the electrically charged spoon and cling to it for a time. Some of the electrons pass from the spoon into the puffed rice, until the grains and the spoon havethe same charge. Since, however, like charges repel one another, we have this unusual drama.

Hostile balloons, Science Project

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Hostile balloons

Blow two balloons right up and join them with string. Rub both on a woollen pullover and let them hang downwards from the string. They are not attracted, as you might expect, but float away from each other. Both balloons have become negatively charged on rubbing because they have taken electrons from the pullover, which has now gained a positive charge. Negative and positive charges attract each other, so the balloons will stick to the pullover. Similar charges, however, repel one another, so the balloons try hard to get away from each other.

Water bow, Science Project

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Water bow

Once more rub a plastic spoon with a woollen cloth. Turn the water tap on gently and hold the spoon near the fine jet. At this point, the jet will be pulled towards the spoon in a bow. The electric charge attracts the uncharged water particles. However, if the water touches the spoon, the spell is broken. Water conducts electricity and draws the charge from the spoon. Tiny water particles suspended in the air also take up electricity. Therefore experiments with static electricity always work best on clear days and in centrally heated rooms.

Coiled adder, Science Project

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Coiled adder

Cut a spiral-shaped coil from a piece of tissue paper about 4 inches square, lay it on a tin lid and bend its head up. Rub a fountain pen vigorously with a woollen cloth and hold it over the coil. It rises like a living snake and reaches upwards. In this case the fountain pen has taken electrons from the woollen cloth and attracts the uncharged paper. On contact, the paper takes part of the electricity, but gives it up immediately to the lid, which is a good conductor. Since the paper is now uncharged again, it is again attracted, until the fountain pen has lost its charge.

Pepper and salt, Science Project

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Pepper and salt

Scatter some coarse salt onto the table and mix it with some ground pepper. How are you going to separate them again? Rub a plastic spoon with a woollen cloth and hold it over the mixture. The pepper jumps up to the spoon and remains sticking to it. The plastic spoon becomes electrically charged when it is rubbed and attracts the mixture. if you do not hold the spoon too low, the pepper rises first because it is lighter than the salt. To catch the salt grains, you must hold the spoon lower.